Various techniques have been used to detect shoplifting or the unauthorized removal of objects from protected areas. U.S. Pat. No. 4,870,391 (Cooper) discloses the use of target wafers which contain an electrical circuit and are affixed to displayed objects for sale. These targets can be removed only by an authorized person using a special tool. If a patron attempts to take an object for sale out of the store before the sales clerk has removed the target wafer, the wafer's resonant circuit will be detected by a surveillance system as the patron enters an interrogation zone near the store exit, thereby setting off an alarm. The disadvantage of this system is that the sales clerk must physically remove the target wafers from every object that is to be protected, which tends to slow down the check-out process.
U.S. Pat. No. 5,029,291 (Zhou et al.) discloses a method of protecting against shoplifting in a supermarket wherein there is one interrogation zone next to every check-out counter. The patron places the merchandise to be purchased on a conveyor belt on the check-out counter which is outside of the interrogation zone. The patron must, however, push his grocery cart through an interrogation zone located adjacent the check-out counter. This system is disadvantageous in that: (1) it requires a separate interrogation zone for every check-out counter, which could require as many as 20 or more pairs of detection panels for a single store, and (2) it can be difficult to push the cart through the interrogation zone, since the already cramped spacing between adjacent grocery counters is made even more cramped by the addition of a pair of detection panels.
U.S. Pat. No. 4,684,930 (Minasy et al.) discloses the use of a freely rolling cylindrical target deactivator which is mounted in the countertop of the check-out counter. This system is disadvantageous because it requires that the target to be deactivated be placed in contact with the cylindrical deactivator. The use of the roller can slow down the check-out process, particularly if it becomes clogged over time due to repeated use. The system is also disadvantageous because it requires that the countertop of the check-out counter be cut into so as to allow the insertion of the cylindrical deactivator.
U.S. Pat. No. 5,059,951 (Kaltner) discloses the use of a deactivator that is fitted into a bar code scanner located in the countertop of the check-out counter. The deactivator includes a pair of single loop antennas which are fitted to the underside of the scanner cover. The antennas are electrically coupled to a matching circuit, which includes the circuitry necessary to develop and receive appropriate signals to deactivate a label by exposing a resonant circuit contained therein to a relatively high energy field sufficient to cause a short circuit in the resonant circuitry of the marker. A control unit provides the signals used to regulate the antenna system. These signals are conveyed by a cable which extends between a transceiver and a casing in the scanner. This system is disadvantageous because of its complexity. The system is also disadvantageous because successful deactivation of the label is dependent both on the speed with which the label is passed over the deactivator and the distance between the label and the deactivator. Thus, in order to provide appropriate assurance that the label has been deactivated, it is usually necessary to include a verification system that confirms that the label has indeed been deactivated.
It would be desirable to have a simplified deactivator which can be easily adapted to fit existing retail store check-out counters, which may or may not employ countertop bar code scanners.